1. Field of the Invention
The present invention relates to a zoom lens consisting of two lens units which is best suited for a lens-shutter camera, a video camera and the like, and more particularly, to a zoom lens with a wide angle of view of about 74.degree. at the wide-angle end and a zooming ratio of about 2.7, which excellently corrects the aberrations and shortens the total lens length (the distance between a first lens plane and an image plane) by appropriately setting the configuration of lenses in the lens units.
2. Description of the Related Art
Recently, the need for a compact zoom lens, whose total lens length is short, has increased with downsizing of a lens-shutter camera, a video camera and the like. In particular, it is requested that a zoom lens be attached to a compact camera such as a lens-shutter camera in which no lenses are interchanged, and there are strong demands for a compact zoom lens having almost the same length as a conventional fixed-focus camera.
In Japanese Patent Laid-Open Nos. 57-201213, 60-170816, 60-191216, 62-56917 and the like, the present applicant proposed a compact and so-called two-unit zoom lens which consists of a first lens unit having a positive refractive power and a second lens unit having a negative refractive power, positioned in the given order from the object side, and which performs zooming by changing the distance between the lens units.
The two-unit zoom lens having high optical performance disclosed in these patent applications arranges a positive refractive power and a negative refractive power in the given order from the object side, achieves a relatively short back focus, and shortens the total lens length.
Furthermore, Japanese Patent Laid-Open Nos. 62-284319, 63-256915, 64-52111, 1-193807 and the like disclose a two-unit zoom lens which consists of a first lens unit having a positive refractive power and a second lens unit having a negative refractive power, and performs zooming by moving both of the lens units forward while changing the distance between the lens units.
Still furthermore, Japanese Patent Laid-Open Nos. 2-50118, 2-71220, 2-190812, 4-145408 and the like disclose a two-unit zoom lens having a relatively high zooming ratio, which consists of a first lens unit having a positive refractive power and a second lens unit having a negative refractive power, and performs zooming by changing the distance between the lens units.
In the above-mentioned two-unit zoom lenses consisting of a first unit having a positive refractive power and a second lens unit having a negative refractive power, it is necessary to appropriately set the layouts of lenses in the lens units in order to achieve good correction of distortion on the wide-angle side, to downsize the total lens system while ensuring a predetermined amount of light on the periphery of the image plane, to obtain a wide field angle of about 74.degree. at the wide-angle end and a zooming ratio of about 2.7, and to maintain high optical performance over the entire zoom range.
Generally, the zooming ratio of such a two-unit zoom lens can be easily increased by increasing the refractive powers of the first and second lens units, which decreases the moving amount of the lens units in zooming, and shortens the total lens length. However, if the refractive powers of the lens units are simply increased, the changes in aberration resulting from zooming are increased, and made difficult to correct.